The breast milk of mothers with premature babies has different amounts of key molecules than that of mothers with babies born at term which may help premature babies catch up in growth and development, say, researchers.

In a study, researchers compared the breast milk of mothers with babies born prematurely -- between 28 and 37 weeks gestation -- and at term -- after 38 weeks.

They examined whether there were differences in the composition of the breast milk' microRNAs, snippets of RNA that affect gene expression and can be passed to the infant.

"We found that there are differences in these microRNA profiles and that the majority of the altered microRNAs influence metabolism," said Molly Carney from Pennsylvania State University College of Medicine in the US.

"If those microRNAs are being transferred to the infant, that could potentially impact how the newborn processes energy and nutrients," Carney said.

The results -- published in the journal Pediatric Research -- could help better match babies with donated breast milk and give an insight into how to develop better infant formula.

Babies born prematurely are at risk of a host of problems, including failure to thrive and neuro-developmental delays.

They also tend to be born at a lower weight than term infants. Because of these issues, premature babies have different nutritional needs than babies born at term.

In this study, the researchers identified nine microRNAs that were significantly different in the premature breast milk.

They found that these microRNAs target metabolic processes and may help regulate gastrointestinal function and energy use in premature babies.